Hi aspirant

No you can't admission in any IIT or NIT without appeard in jee main. Process for admission in any IIT or NIT is first Clear the JEE main exam. After that if you clear the JEE main then only you can appears for the JEE Advance exam. If you clear the Advance then you can get admission in IIT or NIT. Without clear the Advance exam also you can get admission in some of NIT if your JEE main score is good enough But admission in IIT you have to clear the Advance. And without JEE main both are impossible.

I hope it helps you.